According to the scriptures, Cain was “cursed from the earth” for killing his brother Abel (Genesis 4:11). The Bible spells out the specific contours of this curse: “When thou tillest the ground, it shall not henceforth yield unto thee her strength; a fugitive and a vagabond shalt thou be in the earth” (Genesis 4:12). In other words, Cain was no longer able to perform the agricultural farm labor that had been his livelihood until that point (see Genesis 4:2). This curse is a natural continuation of the consequence on Cain’s father, Adam, after eating the fruit of the tree of knowledge of good and evil. Then the Lord said, “Cursed is the ground for thy sake; in sorrow shalt thou eat of it all the days of thy life; thorns also and thistles shall it bring forth to thee; and thou shalt eat the herb of the field; in the sweat of thy face shalt thou eat bread, till thou return unto the ground; for out of it wast thou taken: for dust thou art, and unto dust shalt thou return” (Genesis 3:17–19).

Whereas the ground is cursed because of Adam such that he needs to work hard to get food from it, Cain is cursed from off the ground such that no matter how hard he works, he will not be able to induce the ground to produce food. Note that there is no reference anywhere in Moses or Genesis connecting Cain’s curse to a ban on receiving priesthood authority.

The mark that God placed on Cain is not specified in Genesis, Moses, or anywhere else in the scriptures. It was a sign to others that in spite of what Cain had done, it was not legally appropriate to kill him in retribution. The Lord placed the mark on Cain as an act of mercy, showing to the world that Cain was under the Lord’s protection.